A human body has pieces of biometric information by which an individual is identifiable, and several of them are used as information for specifying and authenticating an individual. For example, a fingerprint, a retina or an iris in an eye, a face, a blood vessel, or DNA (DeoxyriboNucleic Acid) is known as biometric information used for authentication.
With recent progress of a biometrics authentication technique, various apparatus for performing individual authentication by recognizing the characteristics of such a living body which is a part of a human body are provided. With biometrics authentication, authentication is performed by comparing biometric information (registered template) acquired at registration time and biometric information acquired at authentication time.
In order to improve the accuracy of authentication by biometric information, it is desirable to acquire biometric information with constant accuracy every time authentication is performed. However, when authentication is performed, a user who is an object of authentication does not always assume a proper posture.
In addition, some biometric information changes with the lapse of time, so the use of some of biometric information registered once results in a decrease in the accuracy of authentication. Accordingly, the following identity specification apparatus is proposed. When biometric information is acquired, reregistration is performed. By doing so, registered biometric information is updated (see, for example, Japanese Laid-open Patent Publication No. 11-167632)
Usually the accuracy of authentication by a biometrics authentication apparatus decreases when proper biometric information fails to be acquired at biometrics authentication time or when the quality of a registered template is not good. A biometrics authentication apparatus recovers a decrease in the accuracy of authentication by retrying to acquire biometric information from a person who is an object of authentication. In many cases, however, it is difficult to correct unconscious habitual operation of a person who is an object of authentication, for example, in the operation of spreading a palm over a sensor unit at the time of palm vein authentication.
Furthermore, when a registered template is acquired, a proper posture is not always assumed. If inadequate biometric information is registered, a biometrics authentication apparatus fails to realize sufficient authentication accuracy at the time of authentication performed later.
Such a decrease in the accuracy of authentication leads to an increase in the number of retries made to acquire biometric information. As a result, such a biometrics authentication apparatus may be hard to use for a person who is an object of authentication.